As others have mentioned, you should use a transfer switch. Two things that can go bad- 1. IF you accidentally turn on the mains, you will need to call the fire department and possibly an ambulance. 2. Your house wiring to receptacle is usually 12 gauge on older homes and 16 gauge on some newer homes. 12 gauge wires are good for 20 amps. Volts times amps = watts. 120 x 20 = 2400 watts. If you load down your 5,000 watt generator, it will try to give you full power. Even with the best case scenario of 12 gauge wires, this will heat up and burn the wires in your wall because the breaker is on the other end of your circuit, not protecting you.